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Nutrition and immunity

Nutrition and immunity Posted on 8 May, 2020Leave a comment

Back at the beginning of March, I came across some nutrition chatter on social media about how wrong it is call certain foods and nutrients immuno-boosting. This is because if the immune system is ‘boosted’, then it will be sent to overdrive, which only happens when infection occurs. The was in direct rebuttal to the false promises and faddish ideas about how supplements or maybe even IV drips may combat or prevent infection.

But before this all happened, even the nutrition world used this term casually, as I found from the British Nutrition Foundation’s website. I worked there for 6 years, so I know how careful they are with wordings as such… “BNF’s guide to germ killing, immune boosting nutrients to help you stay healthy this winter” (this has since been taken offline)

Perhaps it was just a careless slip as mistakes often happen. But this is just a reflection of how these ideas are not uncommon even for nutritionists who wrote this. This is because even approved health claims, designed for food and supplement labelling purposes, contain rather similar wordings. For example:

Vitamin C is important for the normal functioning of the immune system

For me as good practice, I always cross-check the wordings with the EU health claims register even if it is often very mundane.

It would take a trained eye to understand the subtle differences, and this could be very easily misunderstood by the public. After all, one might argue, that it is a ‘play of words’.

I can appreciate that when people feel run-down, they might feel the need to boost their immune system. This word is also commonly used to describe energy levels too, as if we are a machine and could work with a starter button.

I do think part of the problem is because of how the nutrition discipline has evolved throughout the years. It began as an enquiry to identify the role of nutrients in our body, but became a very much ‘reductionist’ approach to food and health, based on understanding nutrients (oh the whole business of ‘wellness’ is another problem!), let alone the complex reasons on why we eat.

I’ve always struggled to address this meaningfully because as a society we are also used to the ‘nutritionist speak’. It wasn’t until a few years back when I started meeting other food scholars through my MA course and other associated events in the Anthropology of Food at SOAS, which allowed me to rethink about my work and the direction it heads… and hopefully use it as a platform to apply ‘what the science says’ in the ‘context of real life’.

So in response to a couple of queries on nutrition and immunity, this is a press release that I wrote (on behalf of my new client Kurami UK):

It can be quite misleading to think that any food or nutrients are immuno-boosting, as some supplements may suggest. Our immune system is only stimulated when the body senses an infection which then sends signals to the rest of the body which makes us feel run-down. So it will be inaccurate to say we can take a certain supplement to ‘boost’ our immunity.

However, this is not to discount the importance of a healthy, varied diet. Eating a balanced diet provide essential nutrients which work in different ways to maintain the normal function the immune system. This is a key message we want to get across. The nutrients are:

The minerals:

  • iron, found in red meat, beans, pulses, nuts and seeds, fish, quinoa
  • selenium, found in Brazil and cashew nuts and meat
  • zinc, found in meat, poultry, cheese, shellfish, nuts and seeds

The vitamins:

  • vitamin A, found in orange-coloured fruit and vegetables, such as carrots, sweet potato butternut squash and dark green leafy vegetables
  • certain B vitamins
  • vitamin B6, found in poultry, fish, fortified breakfast cereals, soya beans and sesame seeds
  • vitamin B12, found in meat, fish, shellfish, dairy products and fortified breakfast cereals
  • folate, found in green leafy vegetables, pulses, oranges, nuts and seeds, cheese and fortified breakfast cereal
  • vitamin C, found in citrus fruits, berries, kiwifruit, green vegetables, sweet peppers and tomatoes
  • vitamin D, found in oily fish, eggs, fortified breakfast cereals and fortified spreads and dairy products. Note that the most important source of vitamin D is from sufficient exposure to sunlight during UK summer months, but dietary sources of vitamin D can help contribute as well. It has also been suggested that during the winter months, everyone should take a vitamin D supplement because levels are so low in the UK.

In terms of combining nutrients, all I can say is:

  • Vitamin D is important for calcium and phosphorus metabolism.
  • Vitamin C from fruit and vegetables helps with the absorption of the type of iron from plant sources (non-haem) when eaten at the same meal.

I would also add that there is no sufficient evidence which shows supplementation can help to reduce the risk of a viral infection, but a healthy, varied diet helps to promote the normal functioning of an immune system, which is always important. 

Further questions:

What are the benefits of iron, selenium and zinc in regards to health and immune system?

Iron helps to maintain the health of the immune cells. There are mainly two types of iron, haem iron which comes from meat sources, and is better absorbed by the body thatn non-haem iron from plant sources. Vitamin C from fruit and vegetables helps the body absorb plant non-haem iron, when eaten at the same meal.

Selenium is important for producing new immune cells and to strengthen the body’s response to infection.

Zinc helps to produce new immune cells, and helps to develop ‘natural killer cells’ that fight off viruses. It also supports the communication between immune cells, making sure they function properly.

What are the benefits of orange coloured vegetables (vitamin A)?

Orange-coloured vegetables contain beta-carotenes that the body converts to vitamin A. It is vital in supporting T cells, a type of white blood cell that helps to identify infectious bacteria and viruses as part of the body’s immune defence mechanism.

What are the benefits of vitamin D?

Low levels of vitamin D in the body is linked with a reduced immune response. Our body produces vitamin D mainly through the action of sunlight during summer months (strongest between 11am to 3pm) in the UK (from about March/April to September), as the sun has to be high enough in the sky for the ultraviolet B radiation (UVB) to get through to us.

It can be difficult to get sufficient vitamin D through the diet, so it is recommended that we consider taking a supplement of 10 micrograms each day if we are not spending enough time outdoors during self-isolation, or during winter months in the UK.

Further to this vitamin D is important for the body to regulate its use of calcium and phosphorus, which keep bones, teeth and muscles strong and healthy.

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